Known in the art is a surface acoustic wave sensor which uses a surface acoustic wave element to measure the property of a liquid sample or ingredients of a liquid sample.
A surface acoustic wave sensor is comprised of a piezoelectric substrate on which is provided a detection part which reacts with an ingredient contained in a liquid sample on. It measures an electric signal based on a surface acoustic wave (SAW) which is propagated through this detection part to there by detect a property or an ingredient of the liquid sample.
A SAW is generated by an IDT electrode comprised of a pair of comb-shaped electrodes which are provided on an upper surface of the piezoelectric substrate. To prevent the IDT electrode from being immersed in the liquid sample, it is known to provide a sealing member which forms a closed space over the IDT electrode (for example, Patent Literature 1).
The sealing member has a partition wall which is supported on the upper surface of the piezoelectric substrate between the IDT electrode and the detection part. Due to this, the flow of the liquid sample onto the IDT electrode is suppressed. In this way, conventionally, the flow of the liquid sample is controlled by a channel wall.
However, the control of the flow of the liquid sample by the channel wall causes various inconveniences. For example, the partition wall which is positioned between the IDT electrode and the detection part becomes a primary factor of propagation loss of the SAW when the SAW is propagated from the IDT electrode to the detection part.
Further, for example, if the liquid sample is allowed to flow onto the IDT electrode and the channel wall is positioned outside the detection part and the IDT electrode, the liquid sample running along the channel wall causes the liquid sample to flow on the IDT electrode prior to on the detection part. As a result, air bubbles were liable to form on the detection part.
Therefore, it has been desired to provide a surface acoustic wave sensor capable of suitably controlling the flow of a liquid sample.